Consumer Panel Size in Sensory Cosmetic Product Evaluation: A Pilot Study from a Statistical Point of View

Abstract

Subjective evaluations are nowadays applied more commonly in cosmetic product assessment. They are used in quality control, product development steps and efficacy studies for claim support. Several studies have been published to determine the adequate number of panelists, but recommendations and guidelines dealing with this topic are rare in the cosmetic sector. The aim of the present pilot study was to recommend a suitable study plan and define the adequate consumer panel size for cosmetic consumer assessment. A questionnaire-based product evaluation study, with three different cosmetic products, was organized as a consumer test using a seven-point scale. As a last step, a specific statistical calculation was performed to define the minimum sample size. It showed that the minimum sample size, besides the obvious statistical parameters of standard deviation and confidence interval, also depends on age and gender of the panelists and product assessment item. Utilizing a CI of 95% a minimum of 60 panelists seems to be sufficient for home-use-test (HUT) with a given seven-point scale. A minimum of 101 panelists are shown to be sufficient utilizing a CI of 99%.

Five dimensions of cleansing: A holistic view on the facets and importance of skin cleansing

“…Several studies have shown that skin cleansing and bathing products have the potential to improve mood, provide well-being and affect the human psychological state [42][43][44]. To generally evaluate emotions under cosmetic application the objective emotional assessment (OEA) was developed [45].…”

“…Whereas powerful 'instruments' such as OEA exist to evaluate the short-term effects of single cosmetic products on a single psychophysiological effect, like relaxation [43], activation [44] or stress reduction [42,46], up to now no superordinated study (or no adequate combination of 'instruments') has been published to evaluate long-term and holistic effects of skin cleansing on consumers quality of life and well-being. Therefore, an adequate combination of 'instruments' such as OEA and QoL assessments applied over a reasonable time period should be considered in future research on skin cleansing, bathing and shower procedures.…”

“…To generally evaluate emotions under cosmetic application the objective emotional assessment (OEA) was developed [45]. By means of OEA, it has been demonstrated that a specific aroma‐bath additive can reduce stress in terms of certain psycho‐physiological and metabolic endpoints [42]. The same research collaboration has revealed that bath additives can induce relaxation or vice versa stimulate and activate [43].…”

Efficient Development of Green Emulsifier/Emollient-Based Emulsion Vehicles: From RSM Optimal Experimental Design to Abridged In Vivo Assessment

“…However, instruments can miss some subjective aspects despite the fact that they provide quantitative information and accurately measure product characteristics, so sensory studies should supplement rheology and texture analysis [ 21 ]. For this reason, subjective surveys of cosmetic products are standard practice because there is a critical need for direct consumer feedback [ 22 ]. Ideally, cosmetic products should perfectly meet the sensory expectations of consumers, who usually select a skin care product for its function and promising efficacy but are mostly seduced by the pleasantness it brings [ 23 ].…”

“…Ideally, cosmetic products should perfectly meet the sensory expectations of consumers, who usually select a skin care product for its function and promising efficacy but are mostly seduced by the pleasantness it brings [ 23 ]. In consumer sensory studies, the assessors evaluate the intensity of product attributes or the reaction of a particular body area [ 22 ]. The results of the assessment, correlating instrumental measurements, can be a very effective tool for predicting consumer responses.…”